Cross-namespace communication in Kubernetes - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Kubernetes namespace?

A namespace in Kubernetes is like a separate room in a big house. It helps organize and isolate resources like pods and services so they don't mix with others.

beginner

How can pods in one namespace communicate with pods in another namespace?

Pods can talk across namespaces by using the full service name, which includes the service name and the namespace, like service-name.namespace.svc.cluster.local.

beginner

What is the default DNS format to access a service in another namespace?

The format is <service-name>.<namespace>.svc.cluster.local. This tells Kubernetes exactly where to find the service.

intermediate

Why might you want to restrict cross-namespace communication?

To keep things safe and organized, you might limit communication so only certain namespaces can talk to each other. This helps prevent mistakes or security problems.

intermediate

How can Network Policies help with cross-namespace communication?

Network Policies can control which pods in one namespace can connect to pods in another. They act like traffic rules to allow or block communication.

What is the correct DNS name format to access a service named 'web' in namespace 'frontend'?

A web.frontend.svc.cluster.local

B frontend.web.svc.cluster.local

C web.svc.frontend.cluster.local

D frontend.web.cluster.local

The correct format is service-name.namespace.svc.cluster.local, so 'web.frontend.svc.cluster.local' is correct.

By default, can pods in different namespaces communicate without extra configuration?

A Yes, they can communicate using service DNS names

B No, communication is blocked by default

C Only if they are in the same node

D Only if Network Policies allow it

By default, Kubernetes allows cross-namespace communication using service DNS names unless Network Policies restrict it.

What Kubernetes feature can restrict cross-namespace pod communication?

A ConfigMaps

B Namespaces

C Network Policies

D Persistent Volumes

Network Policies define rules to allow or block traffic between pods, including across namespaces.

If a pod in namespace 'A' wants to call a service in namespace 'B', what must it use?

A Only the service name

B The full service DNS name including namespace

C The pod IP address

D The node IP address

Using the full DNS name with the namespace ensures the pod finds the correct service in another namespace.

What is a simple way to test cross-namespace communication?

A Create a ConfigMap

B Restart the Kubernetes cluster

C Delete the namespace

D Use a pod in one namespace to ping a service in another namespace

Testing with a ping or curl command from a pod in one namespace to a service in another shows if communication works.

Explain how pods in different Kubernetes namespaces can communicate with each other.

Think about how Kubernetes DNS helps find services across namespaces.

Describe how Network Policies can control cross-namespace communication and why this might be important.

Consider how you keep different teams or apps separated safely.